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Theses and Dissertations

5-2015

The Effect of Physical Activity Levels on HydrationMarkers in Non-Athletic Free-Living IndividualsMikell Lucas HammerUniversity of Arkansas, Fayetteville

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Recommended CitationHammer, Mikell Lucas, "The Effect of Physical Activity Levels on Hydration Markers in Non-Athletic Free-Living Individuals" (2015).Theses and Dissertations. 1082.http://scholarworks.uark.edu/etd/1082

The Effect of Physical Activity Levels on Hydration Markers in Non-Athletic Free-Living

Individuals

The Effect of Physical Activity Levels on Hydration Markers in Non-Athletic Free-Living

Individuals

A Master’s Thesis submitted in partial fulfillment

of the requirements for the degree of Master of Science in Kinesiology

by

Mikell L. Hammer

Southern Arkansas University Bachelor of Science in Exercise Science, 2013

May 2015 University of Arkansas

This thesis is approved for recommendation to the Graduate Council. Dr. Stavros Kavouras Dr. Matthew Ganio Thesis Director Committee Member Dr. Michelle Gray Committee Member

ABSTRACT

Higher levels of physical activity requires increased fluid intake due to increased water losses via

sweating. PURPOSE: To determine the effect of physical activity on hydration status and water

intake. METHODS: This study involved 8 visits to the Human Performance Laboratory over 22

days. Body weight and urine measurements were taken every visit. Physical activity was

assessed by the International Physical Activity Questionnaire (IPAQ), water intake by the Water

Frequency Questionnaire (WFQ), and hydration status by urine osmolality (UOsm), urine

specific gravity (USG), and urine color (UC). From the IPAQ subjects were classified as low,

moderate and high physical activity levels and the total amount of physical activity was

expressed as MET-min∙w-1. All values represent means across 22 days of measurements except

physical activity and water intake, which was a mean of two measurements. Participants were

excluded if they exercised more than 4 hours a week or if they were on medications that effected

fluid balance. One-way analysis of variance was computed to determine differences in hydration

status between groups. Additionally, 2-tailed Pearson correlations were computed to determine

relationships between all measurements while using physical activity as a continuous variable

(i.e., MET-min∙w-1). RESULTS: 95 participants (45 males, 40±13.2 y, 1.76±0.07 m, 27.3±10.8

%BF 25.9±4.6 kg∙m2; 50 females, 41.1±14.8 y, 1.63±.06 m, 35.0±11.0 %BF, 26.6±6.2 kg∙m2)

completed the study; n=39 for low activity (822±698 MET-min∙w-1), n=48 for moderate activity

(1791±1195 MET-min∙w-1), n=8 for high activity (4,728±1150 MET-min∙w-1). Hydration status

and water intake did not differ across all levels of physical activity; UOsm: 587±209, 596±223,

562±290; and TWI: 2.6±.9, 2.9±1.4, 3.0±1.5 L for low, moderate, and high physical activity

levels, respectively (P≤0.05). UOsm (589±290) was strongly correlated to Total Water Intake

(2.83±1.22 L, P=0.000), and weight (76.4±17.3 kg, P=0.000) at a significance level of P≤0.01

but not strongly correlated to MET∙min∙w-1 (1640±1453). CONCLUSION: No significant

differences in hydration or water intake were observed across groups. However, the small

numbers of participants in the high physical activity levels may have made this comparison

difficult. A wider range of MET-min∙w-1 between groups may need to be studied.

ACKNOWLEDGEMENTS

Special thanks are due to Dr. Kavouras, Dr. Gray, and Dr. Ganio for advising me through the

degree and being a part of the committee. Also, a special thanks goes out to Dr. Johnson and the

research team for mentoring me and making this all possible while giving me the opportunity to

gain valuable knowledge and learning from great experiences.

TABLE OF CONTENTS

Introduction……………………………………………………………………………………….1

Methods…………………………………………………………………………………………...3

Participants………………………………………………………………………………..3

Research Design…………………………………………………………………………..4

Measures…………………………………………………………………………………..4

Procedure………………………………………………………………………………….5

Water Frequency Questionnaire………………………………………………......6

Hydration Markers………………………………………………………………...7

International Physical Activity Questionnaire…………………………………….7

Statistical Analysis………………………………………………………………………...8

Results…………………………………………………………………………………………….8

Discussion………………………………………………………………………………………..22

Limitations……………………………………………………………………………………….24

Conclusion……………………………………………………………………………………….24

References………………………………………………………………………………………..26

Appendix…………………………………………………………………………………………28

1

Introduction: Water is one of the most important nutrients in the human body (Sawka,

Cheuvront & Carter III, 2005). It is the largest component of the human body accounting for

about 50-70% of total body mass according to Maughan (2003), Sawka and colleagues (2005),

and Armstrong (2005). It is crucial for metabolism, temperature regulation, and several other

physiological functions (Armstrong, 2005). Research has found that fluid loses of only 1-2% has

its negative effect on the body including alertness, work performance, headaches, concentration,

and tiredness along with several other health issues (Maughan, 2003). However, it is often

ignored in the general population’s nutrition to replace water loss appropriately (Sawka et al.,

2005). Due to it being ignored, recommendations are often not met. The recommended adequate

intake of water is found to be about 3.7L a day for adult men and 2.7 L a day for adult females

(Dietary Reference Intake for Water, 2005). Water intake includes drinking water, water in

beverages, and water in food (Sawka et al. 2005). Fluids from drinking water and beverages

provide about 81% of total water intake, and water from food provides about 19% of total water

intake according to the Dietary Reference Intake for Water (2005). Urinary loss is the major

route of water loss followed by sweat loss, respiratory loss, fecal loss, insensible loss, and

metabolic production (Armstrong, 2005). Water loss or lack of appropriate total water intake can

result in body water deficits. Body water deficits result when fluid intakes are reduced or fluid

losses are increased (Sawka et al., 2005).Water intake will be assessed using the Water

Frequency Questionnaire (WFQ). Westerterp (1999) found that self-reported dietary records

show an underestimate of actual consumption of fluids and food by about 17% the first week,

27% the second week, and 35% the third week when compared to 2H and 18O. This could be due

to the participant not accurately recalling what they have eaten when the intake is recorded

(Westerterp, 1999). However, it is the next best tool to use to assess water intake. To measure

2

hydration, urine specific gravity, urine osmolality, and urine color will be used to discover if

each individual is euhydrated or hypohydrated. These methods have been used in most hydration

research in the past to determine hydration status including Volpe and colleagues (2009),

Kavouras and colleagues (2012), and Cleary and colleagues (2012). Aside from hydration,

another major health concern that is often ignored is physical activity which can lead to a

healthier longer life or the lack of can lead to obesity, hypertension, diabetes, arthritis,

dyslipidemis, depression, osteoporosis, cancer, as well as several other health concerns (Marcos

et al., 2014). Several studies have found no change in total water intake with age or gender

(Bossignham, Carnell & Campbell, 2005; De Castro et al., 1992). However, there are changes

seen with physical activity. If physical activity is vigorous, total water intake requirements may

exceed 6 L a day (Sawka et al. 2005). To maintain and promote good health, healthy adults aged

18-65 years need moderate aerobic physical activity for a minimum of 30 minutes on five days a

week, vigorous aerobic physical activity for a minimum of 20 minutes on three days a week, or a

combination of the two (Haskell, Lee, Pate, Powell and Blair, 2007). Using the International

Physical Activity Questionnaire (IPAQ) scoring protocol, this physical activity would place an

individual at a minimum of 600 MET-minutes/week which is in the Moderate Intensity category

of physical activity (IPAQ Scoring Protocol, 2005). Reports indicate that as age increases

physical activity decreases and the fluid regulatory capacity decreases due to reduced renal

concentration and diluting capacity partnered with less thirst drive (Armstrong, 2005). Therefore,

we should see a decline in physical activity and lack of replacing fluids properly with an increase

in age. Also, physical activity and environmental exposure will increase water losses and

therefore increase daily fluid needs (Dietary Reference Intake of Water, 2005). We will assess

this using the IPAQ Short Form. Research has shown that the self-report short form IPAQ is a

3

valid instrument for physical activity assessment (Heesch, van Uffelen, Hill & Brown, 2010).

The IPAQ has reasonable measurement properties for monitoring population levels of physical

activity among 18 to 65 year old individuals in diverse settings (Craig et al., 2003). Water

balance studies suggest that going from minimal activity to sedentary activity levels in

temperate environments increased daily water requirements from about 2.5 to 3.2 L/day,

respectively (Fusch et al., 1998; Leiper et al., 1996).Water turnover studies indicate that

individuals with more vigorous levels of activity (> 60 minutes per day of activity)

compared to individuals engaging in relatively sedentary activity (i.e., less than 60 minutes

per day of activity) in temperate environments have increased daily total water

requirements of approximately 3.0 to 4.5 L/day in men (Fusch et al., 1998; Leiper et al.,

1996). Higher levels of physical activity further increase water requirements; for example,

very active fire fighters had daily water requirements of about 7 L/day (Ruby et al., 2002).

Hydration and physical activity are both very important concepts that when combined can

promote well-being and health or be detrimental to the individual. The purpose of the present

study was to study the effects of physical activity on hydration status and total water intake in

healthy and active but non-athletic adults. We hypothesize that there will be a negative

correlation between hydration markers and physical activity levels (as physical activity increases,

hydration markers will show more signs of dehydration). More physically active individuals will

sweat and excrete more water and not replace the lost water affectively.

Methods

Participants: This study included 102 individuals ages 18-65 years old from the local Northwest

Arkansas area in an attempt to obtain a representative sample. Once subjects with incomplete

questionnaires or other errors were excluded from the data 95 subjects (45 males, 40±13.2 y,

4

1.76±0.07 m, 27.3±10.8 %BF 25.9±4.6 kg∙m2; 50 females, 41.1±14.8 y, 1.63±0.06 m, 35.0±11.0

%BF, 26.6±6.2 kg∙m2) remained. Participation was based on inclusion criteria such as medical

clearance, healthy and active (but not a competitive athlete), and signed informed consent prior

to the initiation of any trial procedure. Exclusion criteria included inability to understand and

write English, evidence of clinically relevant metabolic, cardiovascular, hematologic, hepatic,

gastrointestinal, renal, pulmonary, endocrine or psychiatric history of disease (based on the

medical history questionnaire), pregnancy or breast feeding, surgical operation on digestive tract

(except possible appendectomy), regular drug treatment within 15 days prior to start of the study,

currently exercising more than 4 hours per week, inability to participate in the entire study,

changes in diet during the last month, or change in weight more than 2.5 kg (about 5 pounds) in

the last month.

Research Design: A random stratified sampling of participants by age group and gender to

represent the population of the United States was used for the study. All participants reported to

the Human Performance Lab at the University of Arkansas. Each participant that completed the

full study received $150.00.

Measures: This project involved 8 visits to the Human Performance Laboratory at the

University of Arkansas over 3 weeks plus one day (i.e., 22 days). Prior to the start of the study

participants met with a scientist for completion of the medical history and informed consent

forms. Morning urine samples were collected to assess hydration status, weekly water intake was

assessed using the Water Frequency Questionnaire (WFQ), and weekly physical activity was

assessed using the International Physical Activity Questionnaire (IPAQ). Body weight was

recorded every visit to the closest 100 g using a balance beam (Seca, model: 7701321004, Vogel

& Hamburg,Germany), and standing height was recorded the first visit with a wall-mounted

5

stadiometer (Seca, model: 770, Vogel & Hamburg, Germany). Body weight and height were

recorded with the subjects wearing only their shorts and a t-shirt, with no shoes directly after

they urinate. On the first day, a body composition measurement also took place via the use of

dual x-ray absorptiometry (DXA) scan, (Lunar Prodigy, General Electric Healthcare, Waukesha,

WI). Urine osmolality was measured in duplicate, by freezing point depression (3D3 Advanced

Osmometer, Advanced Instruments Inc, Norwood, MA, USA). Urine Specific Gravity was

measured with a hand held refractometer (ATAGO SUR-NE, Tokyo, Japan) in duplicate. Urine

Color was measured standing in a well-lighted room (temperature 20-22°C) with samples placed

in a clear glass tube against a white background. Urine Color was evaluated using the Urine

Color Chart (UCC). The evaluations were carried out by a trained group of researchers at all

times. These evaluation tools were also done by several past studies including Stearns et al.

(2009), Cleary et al. (2012), Bardis, Kavouras, Arnaoutis, Panagiotakos, and Sidossis (2013), and

Kavouras et al. (2012).

Procedures: This project involved eight visits to the Human Performance Laboratory at the

University of Arkansas over three weeks plus one day (i.e., 22 days). Prior to the start of the

study participants met with a scientist for completion of medical history and consent forms.

Following the briefing, written guidelines were provided with all necessary questionnaires. After

explaining the scope of the study and signing the consent form during the initial meeting of the

first day, the individual completed the medical history questionnaire. Next, the Water Frequency

Questionnaire (WFQ) and the International Physical Activity Questionnaire (IPAQ) were

completed. We then collected a morning urine sample and measured height and weight followed

by a measurement of body fat with dual x-ray absorptiometry (DXA). During the study body fat

and height was measured once, eight morning urine samples were collected in small urine

6

containers that were clearly labeled with the date, individual participant number and the sample

identification code, (i.e., “#1 - Morning”, “#2 - Morning”, etc.). Body weight was measured eight

times directly after the subject urinated, and the WFQ and IPAQ were assessed three times all

assessing the week prior to the questionnaire. The participant’s visits and what data is collected

in each visit (Table 1) serve to explain the study in more detail.

Table 1-Explains when the participants visit the lab each week over the entire study and

what data is collected for each day (DXA, Urine, Weight, IPAQ, and WFQ).

WEEK 1 WEEK

2 WEEK 3 WEEK

4

Day Monday

Tuesday

Friday

Monday Monday Tuesday Friday Monday

Lab Visit

1 2 3 4 5 6 7 8

DXA X

Height X

Urine X X X X X X X X

Weight

X X X X X X X X

IPAQ X X X

WFQ X X

X

Water Frequency Intake Records: The Water Frequency Questionnaire (WFQ) is assessed on

the first, fourth, and eighth visits to assess total water intake (L). The WFQ on the first visit is

used for familiarization. The WFQ on the fourth visit is assessing week one, and on the eighth

7

visit week three. Using this tool, we find the total weekly water consumed (L) and find the

average daily water intake (L). We can then correlate these values to the individual’s hydration

status and physical activity level. The recommended adequate intake of water is found to be

about 3.7L a day for adult men and 2.7 L a day for adult females (Dietary Reference Intake for

Water, 2005). The WFQ assesses water from beverages (milk, juice, alcohol, soft drinks, coffee,

etc.) and food (vegetables, fruits, dairy, starches, etc.).

Hydration Markers: Urine Specific Gravity (USG), Urine Osmolality (UOsm), and Urine

Color are collected on all eight visits. The values are used to find the average hydration status for

each individual and to correlate to the physical activity level and water intake of that individual.

The first four urine samples are to find the average of week one and the last four samples are

used to find the average value for week three. Hydration markers that are used for the study are:

• Urine Specific Gravity (USG) - measures hydration by a refractometer to analyze the

amount of light that passed through a small drop of urine and assess urine specific gravity

(Volpe et al., 2009). The cut off point for euhydration is based on Urine Specific Gravity

less than 1.020 (Sawka et al., 2007). Values equal to or greater than 1.020 indicate

hypohydration (Cleary et al., 2012).

• Urine Osmolality (UOsm) - measures the osmolality of urine by freezing point depression

in an osmometer. A person is in the euhydrated state if less than 700 mOsm/kg of water

or in the hypohydration state is equal to or greater than 700 mOsm/kg of water (Sawka et

al., 2007).

• Urine Color Chart- measures the urine concentration. Most researchers use an 8-level

chart. Values at 4 or lower indicate euhydration, and values greater than 4 indicate

hypohydration (Cleary et al., 2012).

8

IPAQ: The IPAQ short form is scored by High, Moderate, or Low physical activity. These

scores are used in correlation with hydration scores and total water intake. The IPAQ is given on

the first visit for familiarization, the fourth visit to assess week 1, and the eighth visit to assess

week 3. To analyze the IPAQ, walking is equivalent to 3.3 METs, moderate Intensity is

equivalent to 4.0 METs, and vigorous intensity is equivalent to 8.0 METs (IPAQ Scoring

Protocol, 2005). Categorizing of the IPAQ is as follows:

• High physical activity category- an individual must have vigorous-intensity activity on at

least 3 days and at least 1500 MET-minute∙w-1 or 7 or more days of any combination of

walking, moderate or vigorous intensity activities and at least 3000 MET-minutes∙w-1.

• Moderate physical activity category an individual must have 3 or more days of vigorous

activity of at least 20 minutes per day, 5 or more days of moderate activity and/or

walking of at least 30 minutes per day, or 5 or more days of any combination of walking,

moderate or vigorous intensity activity achieving a minimum of at least 600 MET-

minutes∙w-1.

• Low physical activity category an individual must have no activity reported or some

activity but not enough to meet the prior listed categories (IPAQ Scoring Protocol, 2005).

Statistical Analysis: Mean and SD values were computed for all variables to describe the data.

A T-test to look at differences between gender across all variables, A One-way Anova (P≤ 0.05)

was used to compare physical activity level with each variable, and also a post hoc test for

multiple comparisons by using Bonferroni’s method (P ≤ 0.05) with physical activity level in

week 1 as an independent variable, physical activity level in week 3 as an independent variable,

and average physical activity across the study as an independent variable were also computed. A

two-tailed Pearson’s Correlation was calculated for all variable averages (P≤0.05). Linear

9

Regressions were also calculated for all variable averages to analyze patterns of change. The

analysis was performed using SPSS.

Results:

Week 1: For week 1 (Table 2) there was no significant difference between males and females

(45 males, 40±13.2 y, 1.76±0.07 m, 27.3±10.8 %BF 25.9±4.6 kg∙m2; 50 females, 41.1±14.8 y,

1.63±0.06 m, 35.0±11.0 %BF, 26.6±6.2 kg∙m2) in UOsm (639±203, 543±240), USG

(1.016±0.006, 1.014±0.006), UC (3.0±0.79, 3.0±0.86), weight (81.6±16.1 kg, 71.9±17.2 kg),

MET-minutes∙w-1 (2053±2178 MET-min∙w-1, 1297±957 MET-min∙w-1), water from food

(0.51±0.27 L, 0.54±0.26 L) water from beverages (2.8±1.5 L, 2.1±1.0 L), or Total Water Intake

(3.2±1.7 L, 2.7±1.1 L), respectively.

Table 2- Week 1 differences in variables in males and females. TWI- Total Water Intake

(L).

Variable Male Female

Subjects 45 50

Age (y) 40±13.2 41.1±14.8

Height (m) 1.76±0.07 1.63±0.06

Weight (kg) 81.6±16.1 71.9±17.2

%BF 27.3±10.8 35.0±11.0

BMI 25.9±4.6 26.6±6.2

UOsm (mmol/kg) 639±203 543±240

USG 1.016±0.006 1.014±0.006

UC (1-8) 3.0±0.79 3.0±0.86

TWI (L) 3.2±1.7 2.7±1.1

MET-min∙w-1 2053±2178 1297±957

Males and females were combined for the rest of the results as there were no significant

differences between genders and we wanted to keep a large sample in each physical activity

category. There was no significant difference (Table 3) between the low physical activity (n=23),

10

moderate physical activity (n=59), and high physical activity (n=13) categories in UOsm

(595±205, 586±235, 584±227), USG (1.014±0.005, 1.015±0.006, 1.015±0.007), UC (3.0±0.8,

2.9±0.8, 2.7±0.8), weight (75.9±19.3 kg, 75.1±16.6 kg, 83.9±15.9 kg), water from food

(0.46±0.24 L,0.55±0.29 L, 0.50±0.16 L), water from beverages (2.21±0.83 L, 2.49±1.4 L,

2.6±1.9 L) or Total Water Intake (2.65±0.94 L, 3.03±1.49 L, 3.04±1.94 L), respectively.

However, as most would assume, there was a significant difference (P≤0.05) in Met-min∙w-1 as

physical activity level increased from low (533±375 MET-min∙w-1) to moderate (1344±718

MET-min∙w-1, P=0.002), low to high (5052±2029 MET-min∙w-1, P=0.000), and from moderate

to high (P=0.000).

Table 3- Change in variables between physical activity levels during Week 1. *-significant

at the P ≤0.05 Level.

Activity

Level Subjects

UOsm

Mmol/kg USG

UC

(1-8)

Weight

(kg)

TWI

(L)

METs-min∙ w-

1

Low 23 595±205 1.014±0.005 3.0±0.8 75.9±19.3 2.65±0.94 533±375*

Moderate 59 586±235 1.015±0.006 2.9±0.8 75.1±16.6 3.03±1.49 1344±718*

High 13 584±227 1.015±0.007 2.7±0.8 83.9±15.9 3.04±1.94 5052±2029*

A)

y = 0.0446x + 2867.3

R² = 0.0027

0.0

1000.0

2000.0

3000.0

4000.0

5000.0

6000.0

7000.0

8000.0

9000.0

10000.0

0.0 2000.0 4000.0 6000.0 8000.0 10000.0

Wa

ter

Inta

ke

(m

l)

Physical Activity (MET-min∙w-1)

Physical Activity and Water Intake

Series1

Linear (Series1)

11

B)

C)

Figure 1- Correlation of A) Physical Activity (MET-min∙w-1) and Water Intake (ml), B)

Physical activity (MET-min∙w-1) and UOsm (mmol/kg), C) Water Intake (ml) and UOsm

(mmol/kg)

Although not significant, we do see a higher score of UOsm, USG, MET-min∙w-1, water

from beverages and Total Water Intake in males than females. Also, we do see a slight decrease

y = -0.0076x + 600.85

R² = 0.0031

0

200

400

600

800

1000

1200

0.0 2000.0 4000.0 6000.0 8000.0 10000.0

UO

sm (

mm

ol/

kg

)

Physical Activity (METs-min∙ w-1)

Physical Activity and Hydration Level

Series1

Linear (Series1)

y = -0.0427x + 713.81

R² = 0.0735

0

200

400

600

800

1000

1200

0.0 2000.0 4000.0 6000.0 8000.0 10000.0

UO

sm (

mm

ol/

kg

)

Water Intake (ml)

Water Intake and Hydration Level

Series1

Linear (Series1)

12

in UOsm and UC, and a slight increase in weight, water from beverages and Total Water Intake

from low, moderate, to high physical activity levels.

In week 1 (Fig. 2), 31% (n=14) of males, 40% (n=20) of females, and 36% (n=34) total

reached the daily water intake recommendations of 2.7 L for females and 3.7 L for males

(Dietary Reference Intake for Water, 2005). For the recommended percentages of water from

food and beverages we selected participants who were 1% below or above 19% for food to be in

the range seen in past research. 39% (n=37) of participants did not reach the recommended

percentages of water from food intake of about 19% (Dietary Reference Intake for Water, 2005),

and only 17% (n=16) were in the 18-20% range of water from food, 66% (n=63) of the

participants were in the euhydrated state, or less than 700 mmol/kg of water when using UOsm

as the hydration marker (Sawka et al., 2007), and 76% (n=72) of the participants reached the

daily physical activity recommendations of moderate physical activity of 3 or more days of

vigorous activity of at least 20 minutes per day, 5 or more days of moderate activity and/or

walking of at least 30 minutes per day, or 5 or more days of any combination of walking,

moderate or vigorous intensity activity achieving a minimum of at least 600 MET-minutes∙w-1

(IPAQ Scoring Protocol, 2005).

13

Figure 2- Subjects in Week 1 that reached the recommendations. Water from food- (n=16),

euhydrated (n=63), ≥ Moderate Physical Activity (n=72), Total Water Intake in males

(n=20), females (n=14).

Week 3: For week 3 (Table 4) there was no significant difference between males and

females in UOsm (642±234, 543±225), USG (1.017±0.006, 1.014±0.006), UC (3.0±0.87,

3.0±0.76), weight (81.4±15.9 kg, 71.8±17.3 kg), MET-minutes∙w-1 (1972±1818 MET-min∙w-1,

1314±1217 MET-min∙w-1), water from food (0.50±0.28 L, 0.49±0.21 L) water from beverages

(2.3±1.2 L, 2.2±1.0 L), and Total Water Intake (2.8±1.3 L, 2.6±1.1 L), respectively.

Table 4- Week 3 differences in males and females. TWI-Water Intake (L).

Gender Subjects Weight

(kg) UOsm USG

UC

(1-8)

TWI

(L)

METs-min∙ w-1

Male 45 81.4±15.9 642±234 1.017±0.006 3.0±0.87 2.8±1.3 1972±1818

Female 50 71.8±17.3 543±225 1.014±0.006 3.0±0.76 2.6±1.1 1314±1217

Again, there was no significant difference (Table 5) between the low physical activity

(n=30), moderate physical activity (n=52), and high physical activity (n=13) categories in UOsm

(573±225, 606±221, 565±310), USG (1.015±0.006, 1.016±0.006, 1.015±0.009), UC (2.9±0.9,

17%

66%

76%

36%

0% 10% 20% 30% 40% 50% 60% 70% 80%

Water from Food

Euhydration

≥ Moderate Activity

Water Intake for Gender

PERCENT THAT REACH RECOMMENDATION

RE

CO

MM

EN

DA

TIO

NWeek 1 Subjects Reaching Recommendations

Percentage

14

3.0±0.6, 2.8±1.2), weight (75.9±17.8 kg, 75.8±18.0 kg, 79.9±13.7 kg), water from food

(0.45±0.25 L,0.51±0.23 L,0.53±0.29 L), water from beverages (1.97±0.83 L, 2.34±1.20 L,

2.49±1.14 L) and Total Water Intake (2.43±0.97 L, 2.83±1.23 L, 2.94±1.34 L), respectively.

Also, there was a significant difference (P≤0.05) in MET∙min∙w-1 as physical activity level

increased. However, from low (922±1589 MET-min∙w-1) to moderate (1475±772 MET-min∙w-1)

there was no significance (p=0.179), but was a significant difference from low to high

(3853±1917 MET-min∙w-1, P=0.000), and from moderate to high (P=0.000).

Table 5- Differences in variables between physical activity levels in Week 3. *-Significance

at the P≤0.05 level.

Activity

Level Subjects

UOsm

Mmol/kg USG

UC

(1-8)

Weight

(kg)

TWI

(L)

MET-

min∙w-1

Low 30 573±225 1.015±0.006 2.9±0.9 75.9±17.8 2.43±0.97 922±1589*

Moderate 52 606±221 1.016±0.006 3.0±0.6 75.8±18.0 2.83±1.23 1475±772*

High 13 565±310 1.015±0.009 2.8±1.2 79.9±13.7 2.94±1.34 3853±1917*

A)

y = 0.0171x + 2687.6

R² = 0.0005

0.0

1000.0

2000.0

3000.0

4000.0

5000.0

6000.0

7000.0

8000.0

0.0 2000.0 4000.0 6000.0 8000.0 10000.0

Wa

ter

Inta

ke

(m

l)

Physical Activity (MET-min∙w-1)

Physical Activity and Water Intake

Series1

Linear (Series1)

15

B)

C)

Figure 3- Correlation of A) Physical Activity (MET-min∙w-1) and Water Intake (ml), B)

Physical activity (MET-min∙w-1) and UOsm (mmol/kg), C) Water Intake (ml) and UOsm

(mmol/kg)

Although not significant, we do see higher levels of UOsm, USG, MET-min∙w-1, and

Total Water Intake in males than females. Also, we see a slight increase in weight, water from

y = 0.005x + 581.99

R² = 0.0011

0

200

400

600

800

1000

1200

0.0 2000.0 4000.0 6000.0 8000.0 10000.0

UO

sm (

mm

ol/

kg

)

Physical Activity (MET-min∙w-1)

Physical Activity and Hydration Level

Series1

Linear (Series1)

y = -0.0872x + 826.95

R² = 0.1935

0

200

400

600

800

1000

1200

0.0 2000.0 4000.0 6000.0 8000.0 10000.0

UO

sm (

mm

ol/

kg

)

Water Intake (ml)

Water Intake and Hydration Level

Series1

Linear (Series1)

16

food, water from beverages, and Total Water Intake as physical activity increases from low,

moderate, to high physical activity levels.

In week 3 (Fig. 4), 18% (n=8) of males, and 38% (n=19) of females, and 28% (n=27)

total reached the daily water intake recommendations, 47% (n=45) of participants did not reach

the recommended percentages of water from food, and only 6% (n=6) were in the 18-20% range

of water from food, 67% (n=64) of participants were euhydrated, and 68% (n=65) of the

participants reached the daily physical activity recommendations.

Figure 4- Subjects in Week 3 that reached the recommendations. Water from food (n=6),

euhydrated (n=64), ≥ Moderate Physical Activity (n=65), Total Water Intake (n=27),

females (n=19), Males (n=8).

Total Average: For the total average of both weeks (Table 6) there was no significant difference

between males and females in UOsm (641±205, 543±226), USG (1.017±0.005, 1.014±0.006),

UC (3.0±0.75, 3.0±0.72), weight (81.5±16.0 kg, 71.8±17.3 kg), MET-minutes∙w-1 (2012±1821

MET-min∙w-1, 1306±911 MET-min∙w-1), water from food (0.51±0.22 L,0.51±0.21 L) water from

beverages (2.6±1.3 L, 2.2±0.98 L), and Total Water Intake (3.0±1.4 L, 2.6±1.0 L), respectively.

6%

67%

68%

28%

0% 10% 20% 30% 40% 50% 60% 70% 80%

Water from Food

Euhydration

≥ Moderate Activity

Water Intake for Gender

PERCENT THAT REACHED RECOMMENDATION

RE

CO

MM

EN

DA

TIO

N

Week 3 Subjects Reaching Recommendations

Percentage

17

Table 6- Total Average differences in males and females. TWI-Water Intake (L).

Gender Subjects Weight

(kg)

UOsm

Mmol/kg USG

UC

(1-8)

TWI

(L)

METs-

min∙w-1

Male 45 81.5±16.0 641±205 1.017±0.005 3.0±0.75 3.0±1.4 2012±1821

Female 50 71.8±17.3 543±226 1.014±0.006 3.0±0.72 2.6±1.0 1306±911

For the average scores across the entire study there was no significant difference (Table

7) between the low physical activity (n=39), moderate physical activity (n=48), and high

physical activity (n=8) categories in UOsm (587±209, 596±223, 562±290), USG (1.015±0.006,

1.016±0.006, 1.015±0.008), UC (3.0±0.7, 2.9±0.7, 2.8±1.1), weight (75.5±17.8 kg, 76.3±17.2

kg, 81.6±16.4 kg), water from food (0.46±0.18 L,0.54±0.23 L, 0.54±0.25 L), water from

beverages (2.20±0.82 L, 2.43±1.32 L, 2.57±1.31 L) and Total Water Intake (2.64±0.89 L,

2.95±1.38 L, 3.0±1.54 L), respectively. Again, there was a significant difference (P≤0.05) in

MET-min∙w-1 as physical activity level increased from low (822±698 MET-min∙w-1, P=0.000),

moderate (1791±1195 MET-min∙w-1, P=0.000), to high (4728±1150 MET-min∙w-1, P=0.000)

levels.

Table 7- Differences in variables between physical activity levels for the total average

across the study. *-Significance at the p≤0.05 level.

Activity

Level Subjects

UOsm

Mmol/kg USG

UC

(1-8)

Weight

(kg)

TWI

(L)

METs-

min∙w-1

Low 39 587±209 1.015±0.006 3.0±0.7 75.5±17.8 2.64±0.89 822±698*

Moderate 48 596±223 1.016±0.006 2.9±0.7 76.3±17.2 2.95±1.38 1791±1195*

High 8 562±290 1.015±0.008 2.8±1.1 81.6±16.4 3.0±1.54 4728±1150*

Although not significant, higher scores were found for UOsm, USG, MET-min∙ w-1,

water from beverages, and Total Water Intake in males than females. Also, although not

significant, there was a slight decrease in UC, and a slight increase in weight, water from food,

18

water from beverages, and Total Water Intake as physical activity increased from low, moderate,

to high levels. For the average (Table 8), total average UOsm (589±290) is strongly correlated to

total average water from food (0.51±0.22 L, P=0.022) at a significance level of P≤0.05 (2-

tailed), total average water from beverages (2.34±1.13 L, P=0.000), total average water intake

(2.83±1.22 L, P=0.000), total average USG (1.015±0.006, P=0.000), total average UC (2.9±.7,

P=0.000), and total average weight (76.4±17.3 kg, P=0.000) at a significance level of P≤0.01 (2-

tailed) but not strongly correlated to MET-min∙w-1 (1640±1453). Total average USG

(1.015±0.006) is strongly correlated to total average water from food (0.51±0.22 L, P=0.009),

total average water from beverages (2.34±1.13 L, P=0.000), total average water intake (2.83±1.2

L, P=0.000), UOsm (589±290, P=0.000), UC (2.9±0.7, P=0.000), and total average weight

(76.4±17.3, P=0.000) at a significance level of P≤0.01 (2-tailed) but not strongly correlated to

MET-min∙w-1. Total average UC (2.9±0.7) is strongly correlated to total average water from food

(0.51±0.22 L, P=0.002), total average water from beverages (2.34±1.13 L, P=0.000), total

average water intake (2.83±1.2 L, P=0.000), total average UOsm (589±221, P=0.000), and total

average USG (1.015±0.006, P=0.000) at a significance level of P≤0.01 (2-tailed) but not strongly

correlated to total average weight, or total average MET∙min∙w-1. Total average water from food

(0.51±0.22 L) is strongly correlated to total average water from beverages (2.34±1.13 L.

P=0.002), total average water intake (p=0.000), total average USG (1.015±0.006, P=0.009), total

average UC (2.9±0.7, P=0.002) at a significance level of P≤0.01 (2-tailed) and UOsm (589±221,

P=0.022) at a significance level of P≤0.05 (2-tailed) but not strongly correlated to total average

weight or total average MET-min∙w-1. Total average water from beverages (2.34±1.13 L) is

strongly correlated to total average water from food (0.51±0.22 L P=0.002), total average water

intake (2.83±1.2 L, P=0.000), total average UOsm (589±221, P=0.000), total average USG

19

(1.015±0.006, P=0.000), and total average UC (2.9±0.7, P=0.000) at a significance level of

P≤0.01 (2-tailed) but not strongly correlated to total average weight or total average MET-

min∙w-1. Total average water intake (2.83±1.2 L) is strongly correlated to total average water

from food (0.51±0.22 L, P=0.000), total average water from beverages (2.34±1.13 L, P=0.000),

total average UOsm (589±221, P=0.000), total average USG (1.015±0.006, P=0.000), and total

average UC (2.9±0.7, P=0.000) at a significance level of P≤0.01 (2-tailed) but not strongly

correlated to total average weight or total average MET-min∙w-1. Total average weight

(76.4±17.3) is strongly correlated to total average UOsm (589±221, P=0.000), and total average

USG (1.015±0.006, P=0.000) at a significance level of P≤0.01 (2-tailed) but not strongly

correlated to total average weight, UC, MET-min∙w-1, total water intake, water from beverages,

or water from food. Total average MET-min∙w-1 is not strongly correlated with any of the

variables in the study. For the regression, we used physical activity as a continuous variable

instead of placing the participants in the three categories of low, moderate, and high physical

activity. The only significant changes seen over time were as Total Water Intake increased,

UOsm and USG tended to decrease. No changes were seen over time between physical activity

and the other variables.

20

Table 8- Correlations (R- value) of the Total Average for each variable * significance of

P≤0.05, ** significance of P≤0.01

Variable UOsm USG UC Weight TWI WFF WFB MET-

min∙w-1

UOsm 0.977** 0.789** 0.405** -0.375** -0.234* -0.359** -0.032

USG 0.977** 0.861** 0.380** -0.383** -0.266** -0.364** -0.035

UC 0.789** 0.861** 0.145 -0.406** -0.310** -0.382** -0.164

Weight 0.405** 0.380** 0.145 -0.763 -0.073 -0.892 0.156

TWI -0.375** -0.383** -0.406** -0.763 0.467** 0.983** 0.076

WFF -0.234* -0.266** -0.310** -0.073 0.467** 0.311** 0.085

WFB -0.359** -0.364** -0.382** -0.892 0.983** 0.311** 0.083

MET-

min∙w-1 -0.032 -0.035 -0.164 0.156 0.076 0.085 0.083

A)

y = 0.0635x + 2724.1

R² = 0.0057

0.0

1000.0

2000.0

3000.0

4000.0

5000.0

6000.0

7000.0

8000.0

0.0 2000.0 4000.0 6000.0 8000.0 10000.0

Wa

ter

Inta

ke

(m

l)

Physical Activity (METs-min∙ w-1)

Physical Activity and Water Intake

Series1

Linear (Series1)

21

B)

C)

Figure 5- Correlations of A) Physical Activity (MET-min∙w-1) and Water Intake (ml), B)

Physical activity (MET-min∙w-1) and UOsm (mmol/kg), C) Water Intake (ml) and UOsm

(mmol/kg)

The average for the entire study (Fig. 6) consisted of 24% (n=11) of males, and 38%

(n=19) of females, and 32% (n=30) total reached the daily water intake recommendations, 41%

y = -0.0048x + 597.14

R² = 0.001

0

200

400

600

800

1000

1200

0.0 2000.0 4000.0 6000.0 8000.0 10000.0

UO

sm (

mm

ol/

kg

)

Physical Activity (METs-min∙ w-1)

Physical Activity and Hydration Level

Series1

Linear (Series1)

y = -0.0679x + 781.24

R² = 0.1403

0

200

400

600

800

1000

1200

0.0 2000.0 4000.0 6000.0 8000.0 10000.0

UO

sm (

mm

ol/

kg

)

Water Intake (ml)

Water Intake and Hydration Level

Series1

Linear (Series1)

22

(n=45) of participants did not reach the recommended percentages of water from food, and only

14% (n=13) were in the 18-20% range of water from food, 67% (n=64) of participants were

euhydrated, and 59% (n=56) of the participants reached the daily physical activity

recommendations (note: weeks 1 and 3 were averaged together however if one week a subject

was low physical activity and the next week moderate physical activity, that subject would be

placed in the low category because their average did not reach the moderate activity

recommendations).

Figure 6- The average for the entire study (shown beside weeks 1 and 3 for comparison)

consisted of water intake (n=11) of males, (n=19) of females, (n=30) total, water from food

(n=13), euhydration (n=64), ≥ moderate activity (n=56).

Discussion The purpose of the present study was to study the effects of physical activity on

hydration status and total water intake in healthy and active but non-athletic adults. We

hypothesized that there would be a negative correlation between hydration markers and physical

activity levels (as physical activity increases, hydration markers will show more signs of

17%

66%

76%

36%

6%

67%

68%

28%

14%

67%

59%

32%

0% 10% 20% 30% 40% 50% 60% 70% 80%

Water from Food

Euhydration

≥ Moderate Activity

Water Intake for Gender

PERCENT THAT HIT RECOMMENDATIONS

RE

CO

MM

EN

DA

TIO

NS

Week 1, 3 and Average Recommendations

Average Week 2 Week 1

23

hypohydration). The results show that although there was a slight increase towards

hypohydration in hydration markers as well as an increase in water intake as physical activity

increased it was not significant. We believe this is due to the small range of physical activity

level across the three categories low (822±698 MET-min∙w-1), moderate (1791±1195 MET-

min∙w-1), and high (4728±1150 MET-min∙w-1). To put this into perspective, 822 MET-min∙w-1 is

equivalent to running a 6 minute pace for about 8 minutes and 30 seconds 6 days a week. 1791

MET-min∙w-1 is equivalent to running a 6 minute pace for about 18 minutes and 30 seconds 6

days a week. 4728 MET-min∙w-1 is equivalent to running a 6 minute pace for about 50 minutes 6

days a week. Although one may consume more fluids during or after a 50 minute run compared

to an 8 minute and 30 seconds run it is not all that significant. However, if there was a wider

range of physical activity across the three categories we may have seen stronger correlations

between physical activity, water intake, and hydration status. Also, the lack of significance could

also be due to the self-reporting of water intake and physical activity.

For week 1, 3, and the total average there was no significant difference between males and

females in UOsm, USG, UC, Weight, MET-minutes∙w-1, water from food, water from beverages,

and Total Water Intake. Males and females were combined for the rest of the results as there

were no significant differences between genders and we wanted to keep a large sample in each

physical activity category. There was no significant difference between the low physical activity,

moderate physical activity, and high physical activity categories in UOsm, USG, UC, weight,

water from food, water from beverages, and Total Water Intake in week 1, 3, or the total average.

However, as most would assume, there was a significant difference in Met-min∙w-1 as physical

activity level increased from low, moderate to high. Although not significant, we do see a higher

score of UOsm, USG, MET-min∙w-1, water from beverages and Total Water Intake in males than

24

females. Also, we do see a slight decrease in UOsm, UC, and a slight increase in weight, water

from beverages and Total Water Intake from low, moderate, to high physical activity levels. 31%

(n=14), 18% (n=8), and 24% (n=11) of males; 40% (n=20), 38% (n=19), and 38% (n=19) of

females; and 36% (n=34), 28% (n=27), and 32% (n=30) total reached the daily water intake

recommendations in week 1, 3, and total average, respectively. 39% (n=37), 47% (n=45), and

41% (n=45) of participants did not reach the recommended percentages of water from food

intake in week 1, 3, and total average, respectively. Only 17% (n=16), 6% (n=6), and 14%

(n=13) were in the 18-20% range of water from food in week 1, 3, and total average,

respectively.66% (n-63), 67% (n=64),67% (n=64) were euhydrated in week 1, 3, and total

average, respectively. 76% (n=72), 68% (n=65), 59% (n=56) of the participants reached the daily

physical activity recommendations in week 1, 3, and total average, respectively. Based on these

results, there seemed to be a slight decrease in water intake and physical activity between week 1

and week 3. Also, UOsm is significantly correlated with USG, UC, weight, and Total Water

Intake. Total Water Intake is significantly correlated with UOsm, USG, UC, water from food and

water from beverages. Weight could be correlated to hydration status because of the increase (or

lack of) of water in the body. Also, it could be due to muscle gains or food and beverage intake.

The results show that the human body is very efficient at maintaining proper hydration across

various physical activity levels on its own. However, more research needs to be done with higher

levels of physical activity.

Limitations: Self-reported data was administered to the participants via the health history form,

International Physical Activity Questionnaire (IPAQ), and water frequency questionnaire. The

results of this study heavily rely on these results. Therefore, the results could be skewed if the

questionnaires are not completed with accuracy and honesty.

25

Conclusion: Based on our results, there was no relationship between the three levels of physical

activity and hydration and water intake status. Water intake did not significantly increase with

the increase of physical activity, and hydration status did not significantly change either. This

shows the human body can effectively control its own hydration levels to an extent. A larger

range of MET-min∙w-1 needs to be studied. As expected, there was a relationship with hydration

status and water intake. There was an uneven dispersion of participants in the low, moderate, and

high physical activity categories which could be skewing the data of each variable used. In the

future, even dispersion of participants should be a focus. Further research in looking at physical

activity, hydration, and water intake is needed with a larger sample size to even the physical

activity categories and broader range of physical activity level.

26

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Appendix